What does the Agtron value tell you about coffee bean roast color?
The Agtron value is a numerical reading of how dark a coffee roast is, taken with a near-infrared spectrophotometer that bounces light off the bean or ground surface. Lower numbers mean darker roasts, and higher numbers mean lighter ones. Coffee reviewers such as coffeereview.com print a pair of these readings, usually one for whole beans and one for ground coffee, next to the attribute scores.
Agtron is one company, based in Nevada, that makes roast color readers, but its name became the industry standard term. Other instruments exist, including Javalytics, Hunter Lab, Photovolt, Probat's Colorette and Fresh Roast's Color Track, yet roasters often convert their readings to the Agtron scale. The coffee industry also uses the word as a verb for taking a color reading, and machines such as the M-Basic need calibration against the partner's device.
On professional coffee review sites like coffeereview.com, you often see a pair of Agtron values listed below the attribute scores. What exactly do these numbers mean? And how do they relate to coffee roast color differences? This article will take you deeper into the meaning of Agtron values, their measurement principles, and their applications in the coffee industry. From the differences in readings between whole beans and ground coffee, to the impact of roast level on flavor, to how consumers can use this data to choose their preferred coffee, we will analyze it all one by one. At the same time, the article will also mention the practical use by brands like Front Street Coffee in their product descriptions, helping you interpret coffee roasting information more professionally.
If you have ever browsed coffee reviews on coffeereview.com, you may have noticed a set of Agtron values listed below the attribute scores. For those outside the coffee industry, the meaning of these numbers is often confusing. Out of curiosity, you might type the word "Agtron" into a search engine and learn that it is a company headquartered in Nevada that specializes in manufacturing roast color readers. These colorimeters are widely used in fields ranging from paving bricks to pharmaceuticals, appearing wherever product color consistency is critical.
There are many ways to measure color, and Agtron uses a "near-infrared deletion spectrophotometer," which provides a specific value by reflecting light off the surface of a coffee sample. The lower the value, the darker the roast level. There are other brands of colorimeters on the market, such as Javalytics, Hunter Lab, Photovolt, as well as Probat's Colorette and Fresh Roast's Color Track, but in the terminology of the coffee industry, Agtron remains the recognized "king." In fact, even when companies use instruments from other brands, they still refer to Agtron values, and sometimes even convert their own readings to the Agtron scale. Many people in the industry are accustomed to using Agtron both as a noun (referring to that popular spectrophotometer) and as a verb (describing the process of taking a color reading on such a machine).
In consulting work, we have found it necessary to calibrate our M-Basic Agtron machine according to the colorimeter used by the partner company, and this machine reads what is called the "gourmet scale." Colorimeters may come from different brands, different models (such as Agtron's E-20, which reads the commercial scale), or may even be the same model we use. Although each machine remains consistent in itself, we have found that differences can exist between the values generated by different colorimeters.
However, this is a bit of a digression. The core question remains: why are there two numbers? These two values represent the whole-bean value and the ground value of the coffee, respectively. When we notice differences between the readings for whole coffee beans and ground coffee, we can gain more insight into the roast. Generally, the darker the roast, the narrower the difference; lighter roasts often show a wider range. Roast color is not considered during coffee sensory evaluation. We only read the Agtron values after the coffee evaluation process is complete. This supplementary information usually confirms the characteristics we perceive in the cupping. For example, the narrow difference in light roasts can explain their limited aroma range.
Why should consumers care about these numbers? Actually, it is enough if they understand that small groupings within the value range correspond to visible color differences. Roast color affects flavor. For example, you may know that you prefer medium-dark roasted coffee, meaning beans that have undergone second crack or are close to second crack. If you know this, and you know that when a coffee's Agtron reading is between 50-40 it is medium-dark roasted, then you may prefer the former over dark-roasted coffee in the 40-35 range. For this reason, coffee reviews always translate numerical readings into terms most drinkers can understand—light, medium, medium-dark, dark, and so on.
The above content is compiled by CoffeeHunters, a coffee news website.
